This disclosure relates to solid oxide fuel cells. More particularly, this disclosure relates to a multi-layered coating used in solid oxide fuel cells.
Solid oxide fuel cells are known and used for generating electricity. A typical solid oxide fuel cell includes an electrolyte located between the anode and the cathode. A fuel cell stack may include multiple solid oxide fuel cells.
Interconnects are positioned between adjacent solid oxide fuel cells to connect the solid oxide fuel cells in series. The interconnects include channels that deliver fuel and oxygen to the fuel cell.
Some components of the fuel cell stack, such as the interconnects of some fuel cells, include a single-layer coating that suppresses the oxidation rate and prevents chromium containing species from evaporating and poisoning the cell. The coating is typically applied by slurry-based processes, such as a wet spray, a dip, or a screen printing. As known, the base alloys beneath the coating limit the firing temperature that can be used when applying the coating, which may result in pores within the coating. Chromium species, such as oxides or oxide hydroxides, can undesirably evaporate and transport through the pores in the coating. Accordingly, the coating is applied using a plasma spray technology, which can reduce the porosity in the coating, but this process is costly and limited by line-of-sight constraints. In parallel, chromium ions can diffuse through the solid state and coatings that reduce the conductivity of chromium ions through dense matter are needed.